Heat exchanger



Oct. 13, 1936.

B. s. Foss HEAT EXGHANGER' Filed Jan. 18, 1936 I Ill/11111111111]. n

Patented Oct. 13, 1936 UNITED STATES PATENT OFFICE HEAT EXCHANGER Application January 18, 1936, Serial No. 59,705

8 Claims. (Cl. 257-220) The present invention relates to heat exchangers and more particularly to that type of apparatus wherein heat is abstracted from gases, as for example, waste or flue gases, and transferred to a fluid medium, such as water or air.

In apparatus of this general type, of which the economizer and air heater are well known examples, the hot gases are caused to flow through a casing across which extend the water or air tubes. Commonly these are arranged in rows transverse to the gas flow with tubes of adjacent rows staggered, thus causing the gas to flow through the casing in a series of sinuous paths, and thereby bringing the gas into more intimate contact with the tubes to facilitate the transfer of heat.

Ordinarily the side walls of the casing are straight or plane-surfaced, with the result that a straight passageway extends alongside the walls of the casing between the latter and the end tubes of each row through which passageway the hot gases are free to pass without turbulence and the resulting intimate contact the other tubes.

with the end tubes, particularly on their surfaces toward the casing wall, so necessary for the effective transfer of heat. As a result, the end tubes of the rows and particularly those end tubes nearer the casing 'are less efiicient than Moreover, the contact of the hot gases with the walls of the casing transfers to them a very substantial amount of heat, which is consequently rendered unavailable for heating the water or air.

It is the object of the present invention to increase the efiiciency of these end tubes nearer the casing wall by providing them with supplementary or increased heating surfaces, at the same time avoiding to a large extent the losses to the casing wall by so constructing these supplementary heating surfaces that they will form tion, Fig. 1 is a sectional view of an economizer,

including the casing, in which the end tube members or elements of alternate rows are formed of sectional castings, having undulatory inner faces constitutingsupplementary heating surfaces for the water tube which is located in each crest; and Fig. 2 is a similar sectional view of an economizer, the end tube members or. elements of which consist of a tube having longitudinal supplementary heating surfaces or flanges arranged at an obtuse angle, the elements being assembled so that the tubes and flanges form a zigzag casing wall.

The casing of the economizer is of conventional design, composed of a framework of girders 4, which support the walls 6, shown as consisting of steel plates 8' with a filler of heat insulating material Ill. The water tubes I2 may be of steel or cast iron, and are arranged in rows transversely of the passage in the casing, the tubes of one row being in staggered relation to the tubes in anadjacent row to cause the flue gases to flow through the casing in a series of sinuous or zigzag paths. The water tubes l2 are interconnected by the usual headers, not shown, to form a circulating system for the feed water arranged according to conventional practice. The hot flue gases from the furnace or boiler are admitted to the space It below the economizer tubes, and are led away from the space l6 after passing upwardly between, and giving up heat to, the said tubes.

The particular elements of the economizer which embody the present invention are represented in various forms by the tube members l8 and 20 of Fig. 1, and 22 of Fig. 2. Members l8 are preferably of cast iron, and extend the length of the side wall. One side is flat, to fit against the wall 6 to which the members may be secured in any suitable manner. The side of the casting facing the interior of the economizer is formed with a series of undulations substantially as shown by the sectional view.

Each section may have one or more crests and valleys, depending on such factors as weight and size. By use of several castings arranged in a vertical row against the wall, a supplementary side wall will be formed.

In each ridge or crest position 24 of the castings I8 is a longitudinal passage having a steel liner 26. The ends of these liners are connected by headers with the rest of the economizer tubes, so that the passages in the castings are part of the feed-water circulating system, thus utilizing to the fullest degree the heat available in the flue gases.

The side wall castings I8 with steel liners 26 are used in installations which are operated under high feed-water pressure. For installations which are to be operated at low or moderate pressures the steel liners are imnecessary, and the construction illustrated by members 20 may be employed, the water flowing directly in the bores or passages 28 in the castings.

In the construction represented by the memrow adjacent to the side wall 6 have flanges 30 extending the length of the tubes to which they are welded by a continuous weld 32. These flanges are at an obtuse angle to one another and such that the adjacent tips or free edges of the flanges are in contact with one another and also with the flat wall surface 6.

In all these specific forms of the present invention the efliciency of the end tubes is increased by the provision of the supplementary heating surfaces, which absorb heat from the passing gases. Furthermore, by the shape and arrangement of these surfaces not only is the same shape and cross-sectional area of gas passage provided adjacent the walls of the casing, thereby insuring uniform velocity of gas flow throughout the entire width of the economizer, but there is also formed the side wall of the casing from which is transferred to the water in the tubes or passages the heat absorbed by such walls and heretofore lost. Thus the efficiency of the economizer is further increased by pre venting waste of energy and heat.

Although the preferred embodiments of the present invention have been illustrated and described, it is to be understood that the invention is not limited thereto but may be embodied in other forms and arrangements within the language and scope of the appended claims.

Having thus described the invention, what is claimed is:

l. A heat exchanger for extracting heat from gases, comprising a casing forming a passage through which the gases flow, and a plurality of fluid conducting tubes arranged in rows transversely of the passage in the casing, the tubes of one row being disposed in staggered relation with respect to the tubes in an adjacent row, and the end tube of alternate rows being provided with a supplementary heating surface extending longitudinally of the tube and forming when assembled with other similar end tubes an undulatory casing wall to provide a gas passage of substantially uniform cross-sectional area adjacent the wall.

2. A heat exchanger for extracting-heat from gases, comprising a casing forming a passage through which the gases flow, and a plurality of fluid conducting tubes arranged in rows transversely of the passage in the casing, the tubes of one row being disposed in staggered relation with respect to the tubes in an adjacent row, and

the end tubes of alternate rows being formed in sectional blocks having lateral supplementary heating surfaces extending longitudinally of the tubes and forming when the blocks. are assembled in aligned relation an undulatory casing wall to provide a gas passage of substantially uniform cross-sectional area adjacent the wall.

3. A heat exchanger for extracting heat from gases, comprising a casing forming a passage through which the gases flow, and a plurality of fluid conducting tubes arranged in rows transversely of the passage in the casing, the tubes of one row being disposed in staggered relation with respect to the tubes in an adjacent row, and the end tubes of alternate rows being formed in sectional blocks eachhaving an undulatory face and each containing a plurality of fluid conducting passages positioned in the crests of such face, the undulatory face serving as a supplementary heating surface and forming the easing wall to provide a gas passage of substantially uniform cross-sectional area adjacent the wall.

4. A heat exchanger for extracting heat from gases, comprising a casing forming a passage through which the gases flow, a plurality of fluid conducting tubes arranged in rows transversely of the passage in the casing, the tubes of one row being disposed in staggered relation with respect to the tubes, in an adjacent row, and the end tubes of alternate rows having longitudinal flanges to provide supplementary heating surfaces and to close the space between said end tubes to form the casing wall.

5. A heat exchanger for extracting heat from gases, comprising a casing forming a passage through which the gases flow, and a plurality of fluid connecting tubes arranged in rows transversely of the passage in the casing, the tubes of one row being disposed in staggered relation with respect to the tubes in an adjacent row, and the end tubes of alternate rows having longitudinal flanges disposed at an obtuse angle with respect to one another to provide supplementary heating surface and to form an undulating casing wall whereby the gas passage adlacent such wall has a substantially uniform cross-sectional area.

6. A heat exchanger for extracting heat from gases, comprising a casing forming a passage through which the gases flow, and a plurality of fluid conducting tubes arranged in rows transversely of the passage in the casing, the tubes of one row being disposed in staggered relation with respect to the tubes in an adjacent row, and the end tubes of alternate rows having longitudinal flanges disposed at an obtuse angle with respect to one another to provide supplementary heating surface and contacting at their margins to form an undulating casing wall whereby the gas passage adjacent such wall has a substantially uniform cross-sectional area.

7. A heat exchanger for extracting heat from gases, comprising a casing forming a passage through which the gases flow, and a plurality of fluid conducting tubes arranged in rows transversely of the passage in the casing, the tubes of one row being disposed in staggered relation with respect to the tubes in an adjacent row, and the side walls of the casing being of undulating form in the direction of gas flow to provide gas passages of substantially uniform crosssectional area adjacent the walls, the side walls comprising insulating material having their inner surfaces covered by sectional members containing fluid conducting passages.

8. A heat exchanger for extracting heat from gases, comprising a casing forming a passage through which the gases flow, and a plurality of fluid conducting tubes arranged in rows transversely of the passage in the casing, the tubes of one row being disposed in staggered relation with respect to the tubes in an adjacent row, and the side walls of the casing being of undulating form in the direction of gas flow to maintain gas passages of substantially uniform cross-sectional area adjacent the walls, said walls comprising insulating material and tube elements each consisting of a tube having longitudinal flanges disposed at an obtuse angle with respect to one another, the margins of the flanges engaging one another and the insulating material to form the casing wall, with spaces between the insulating material and the tube element.

- BENJAMIN S. F088. 

